Today there are three basic types of power plants for aircraft and in each of these power plants during operation, icing problems may develop necessitating anti-icing equipment. Two of these power plants each use propellers for developing a major portion of the thrust for the aircraft. The internal combustion engine utilizes a propeller with a spinner, whereas the turboprop power plant utilizes a gas turbine engine for driving the propeller to create the thrust, the propeller having a spinner. Both the conventional internal combustion engine and the turboprop engine rotate the propellers and their spinners at relative low speeds below about 2000 rpm. For example, the Rolls-Royce Limited GRIFFIN.RTM. and MERLIN.RTM. internal combustion engines have an operating speed of about 1500 rpm, whereas the Rolls-Royce DART.RTM. turboprop engine and the TYNE.RTM. turboprop engine have operating speeds of 1540 rpm and 960 rpm, respectively. On the other hand, the gas turbine propulsion engine which provides thrust for the aircraft only from flow of exhaust gases or a combination of flow of exhaust gases and by-pass air has operating speeds for its spinner considerably in excess of 3000 rpm. For example, the Rolls-Royce RB211 gas turbine propulsion engine has an operating range of approximately 4500 rpm for takeoff and 3750 rpm for cruise.
In all three power plants described above, the buildup of ice on the components thereof, and in particular on the spinners, must be particularly avoided, otherwise the ice may be shed from the spinner in large pieces causing severe damage to the engine of the aircraft or the ice may build up unevenly on the spinner, thereby resulting in vibrations to the engines. Heretofore, the best method of avoiding or reducing icing problems was to provide the spinner with anti-icing equipment which usually took the form of electrical heating elements in the spinner, the supply of deicing fluid to the outside surface of the spinner, or the supply of hot air to the interior of the spinner. Such anti-icing equipment, while usually quite effective in operation, did add weight and complexity to the engine.
Other efforts have been made to provide automatic anti-icing spinners for propeller driven aircraft, and these included providing a spinner made from a flexible material, the spinner being inflated to its desired shape to provide rigidity to the spinner surface while permitting sufficient distortion of the spinner surface to break up ice deposits. While this type of spinner could probably function in its intended manner on an internal combustion engine or a prop turbo engine wherein the operating ranges of the spinner speed are below 2000 rpm, it would be impractical to use such a spinner on a gas turbine propulsion engine of the conventional or fan jet type wherein thrust is provided only from flow of exhaust gases or a combination of flow of exhaust gases and by-pass air. The high speeds required for the spinners on the gas turbine propulsion engines would not permit the use of an inflated spinner of this type as too high centrifugal forces would be developed in the inflated spinner which would cause the spinner to vibrate and deform excessively and, thus, subject the engine bearings to excessive out of balance forces and unnecessary wear.